It has been observed that cancer cells rely on exogenous glutamine, albeit the degree of dependency varies from cancer to cancer. In these actively proliferating cancer cells, the metabolism of glutamine to lactate, also referred to as “glutaminolysis” is a major source of energy in the form of NADPH. The first step in glutaminolysis is the deamination of glutamine to form glutamate and ammonia, which is catalyzed by the glutaminase enzyme (GLS). Thus, functioning as a control point for glutamine metabolism, GLS may provide a potential new target for the treatment of cancer. Recently, the creation of GLS inhibitors that are specific and capable of being formulated for in vivo use is permitting this hypothesis to be tested. Therapeutic approaches for clinical use of these compounds would be advantageous.